Variable delivery pump



2 SHEETS-SHEET 1 M. A. MATHYS VARIABLE DELIVERY PUMP March 11, 1952 Original Filed Feb. 17, 1941 INVENTOR. mam 5 BY J QM MM aM L v ATTORNEYS March 11, 1952 M. A. MATHYS 2,533,861

VARIABLE DELIVERY PUMP Original Filed Feb. 17, 1941 r r 2 SHEETS-SHEET2 IN V EN TOR.

ATTORNEYS Patented Mar. 11, 1952 2,588,861

UNITED STATES PATENT OFFICE VARIABLE DELIVERY PUMP I Max A. Mathys, Detroit, Mich., assignor to Ex- Cell-O CorporationyDetroit, Mich., a corporation of Michigan Original application February 17, 1941, Serial No. 379,211. Divided and this application November 15, 1946, Serial No. 710,153

6 Claims. (Cl. 103--162) The present invention relates to improvements shaft 16 to establish the drive connection for the in rotary pumps of the swash plate type. pump, and which are relatively short so as to One of the objects of the invention is to provide permit a limited amount of peripheral float of a pump of the foregoing type in which the swash the cylinder body l and thereby ensure accurate plate is controlled to counterbalance the hyseating of the valve faces H and I2. draulic reaction in the pump cylinders, and is fur- Formed in the cylinder body H1 in parallel ther subject to adjustment in response to fluid uniformly spaced relation about the bore 18 are pressure to vary the pump displacement seleca plurality of pump cylinders 2| having cylinder tively from zero to maximum, ports 22 opening from the inner ends to the valve Another object is to provide a variable delivery face I2. Suitable pump pistons 01' plungers 23 swash plate pump which is simple in construcare respectively reciprocable in the cylinders 2|. tion, and capable of sensitive and accurate The plungers 23 are urged outwardly y Coiled control in displacement, compression springs 24. These springs engage Further objects and advantages will become the inner ends of the cylinders 2|, and extend apparent as the description proceeds into bores in the inner ends Of the plungers 23 In the accompanying drawings, so that the latter may be comparatively short in Figure 1 is a fragmentary side view, partially e in vertical section, of a machine unit incorporat- A swash plate 26 having a flat bearing face 21 ing a pump embodying the features of the presis in operative association with the outer ends ent invention. 20 of the plungers 23, and when inclined is adapted Figs. 2 and 3 are views of the pum valve taken to cause reciprocation f h pluns rs in unirespectively in the directions of the arrows 2-2 m y timed S q e p otati n of the nd 3 .3 of Fig, 1 cylinder body l0. Bearing shoes 28 are connect- Fig, 4 is a fragmentary horizontal sectioned ed by means of suitable inserts 29, for universal i t k along 11 4 4 of Fig, 1, pivotal adjustment, to the outer ends of the Fig. 5 is a fragmentary vertical sectional view plungers 23, a d ave flat fac s in S n entaken along line 5-5 of Fig. 4, gagement with the bearing face 21 of the swash Fig. 6 is a diagrammatic representation of the plate The swash Plate 5 is u te in t e pump, I housing 1 on a pivot pin at one' end for The pump, constituting the exemplary embodi- 3Q n ular ju tm n b ut an xi xten i ment of the invention, is shown as incorporated transversely of the axis of rotation of the y in hydraulic power unit disclosed and claimed in der body I0. Preferably, the pin 30 is located at my copending application, Serial No. 379,211, a point adjacent the axis of each plunger 23 as filed February 17, 1941 (now patent No. 2,416,- the latter reaches top dead center position at the 339), of which the present application is a diend of the pressure stroke. As a result, the in-- vision. Consequently, the pump utilizes as its ward limit of movement of the plungers 23 is housing the external housing I of the power substantially constant and close to the inner ends unit. of the cylinders 21.

The pump is of the type having-parallel an- In operation, the pump will discharge connul y arranged P t and cylinder units, and tinuously, and the rate of discharge will be subis mounted on the inside of a gear case 8 closing stantially constant for any given setting of the one end of the housing I. In its preferred form, swash plate 26. If the angular position of the t p p mpr a sta ion ry valve member swash plate 26 is changed, the length of the 9 and a rotary cylinder body l0, having flat anplunger stroke will be adjusted to vary the rate nular end valve faces H and I 2 in rotary bearing 4 and volume of pump displacement. When t e engagement. The valve member 9 has the form plate 26 is adjusted into a plane perpendicular of a cylindrical plug tightly pressed into a bore to the shaft l6, no reciprocation will be im- |3 in the gear case 8, and is located radially by parted to the plungers 23 and the dump dismeans of a spline screw l4 projecting from the placement will be, zero. In the reciprocation of case into a groove I5. The inner end of a drive the plungers 23, those on the suction stroke take shaft 16 extends freely through an axial bore I! in fluid from a line 3|, and those on the presin the valve plug 9 into an axial bore l8 in the sure stroke discharge fluid to a line 32. For fur cylinder body Ill. Formed in the bore l8 are ther details of the pump valve porting, reference internal splines 19 which interfit slidably with may be had to Snader and Mathys Patent No longitudinal splines 20 on the inner end of the 54 ,299,235, issued October 20, 1942.

The swash plate 26 is angularly adjustable about the pin 30 to vary the displacement of the pump. Within the broad aspects of the present invention, such adjustment may be effected by any suitable means. In the present instance, the

swash plate 26 is automatically positioned in response to a predetermined control pressure.

Thus, the plate 26 is automatically adjusted to reduce the pump delivery upon an increase in control pressure, and to increase the delivery upon a decrease in the pressure. means for this purpose comprises a balancing plunger 33 and a control plunger 34 acting on the free end of the swash plate 26 in a direction to level off the latter against the hydraulic reaction in the cylinders'Zl and the action of the return springs 2G.

The pressure balancing plunger 33 (Fig. is reciprocable in a bore 35 formed in the body structure I of the housing and extending transversely of the pin 30. One end of the bore 35 opens toward the free end of swash plate 25, and the other end is closed to define a pressure chamber 36 and is connected through a branch line 3'! to the pressure line 32 of the pump. A shoe 3?: is connected by means of an insert 39 for universal pivotal adjustment to the outer end of the plunger 33, and bears slidably against a fiat face All on the rear of the swash plate 25. The diameter of the plunger 33 and the moment arm of force exerted thereby on the swash plate 26 are such that this force will substantially counterbalance the hydraulic reaction in the pump cylinders 2!. Since the delivery pressure of the pump is always connected through the lines 32 and 3'! to the pressure chamber as at the inner end oi the plunger 33, the swash plate 26 will be hydraulically balanced throughout the range of pump delivery.

The control plunger 36 similarly 'is mounted for reciprocation in a bore Ill formed in the body structure of the housing I and opening transversely of the pin 39 to the rear face 46 of the swash plate 26. A shoe 4?. is connected by means of a suitable insert 43 (Figs. 1 and 4) for universal pivotal adjustment to the outer end of the plunger 34, and slidably engages the face m. A plug id is positioned in the inner end of the bore ll, and limits the inward movement of the plunger 34 to determine the maximum pump delivery. Opening from the inner end of the bore tl, between the plunger 3% and the plug 44, is a pump control line 45. This line may be connected to any suitable source of adjustable control pressure.

In operation, when the control line 45 is exhausted, the swash plate 26 will move into maximum delivery position as determined by the stop plug M. If the control line 45 is connected to a source, as for example, the pump line 32, equal in pressure to or greater than the maximum required control pressure, the swash plate 25 will level off into substantial no-delivery position. If the control line 45 is connected to a source of intermediate control pressure, the swash plate 26 will move into an intermediate position to reduce the pump delivery accordingly, and any variation in the control pressure'will result in a corresponding adjustment of the pump displacement. Since the hydraulic reaction in the pump cylinders 21 is counterbalanced by the plunger 33, the control pressure for normal working demands on the pump can be considerably lower than the pump delivery pressure. While a co paratively low control pressure is. 25

The particular able, it should be sufficiently high to avoid substantial changes in the compressibility of the fluid. I have found that a sensitive control is obtained for low pump delivery, adapted for ex- 5 ample for ordinary feed traverse of a machine tool element, when a control pressure at or above 110 pounds per square inch is employed. It will be understood of course that the range of control pressures required for adjustment of the pump displacement from zero to maximum is influenced by the cross sectional pressure area of the plunger 34, but in any event slight variation of the control pressure from a lesser to a greater pressure can effect a corresponding adjustment of the pump displacement from maxi mum to zero.

I claim as my invention:

1. A pump comprising, in combination, a stationary valve member having an end valve face with peripherally spaced arcuate inlet and outlet valve ports, a rotary cylinder body having a plurality of annularly arranged parallel pump cylinders with end ports opening to an end valve face in flat bearing engagement with said first mentioned face, a plurality of pump plungers reciprocable in said cylinders, spring means for urging said plungers outwardly, an axial shaft for driving said body, said shaft extending freely through said stationary valve member into said body an angular swash plate coacting, with the outer ends of said plungers for reciprocating said plungers in uniformly timed sequence upon rotation of said body, said cylinder ports moving successively through communication with said inlet and outlet ports upon movement of the respective plungers through their intake and pressure strokes, and interfitting splines drivingly connecting said body and the inner end of said shaft, the splines in said body being relatively short and the splines on said shaft being relatively long, said interfitting splines permitting limited relative floating movement of said body to insure uniform surface engagement between said valve faces.

2. A pump comprising, in combination, a stationary valve member having an end valve face with peripherally spaced arcuate inlet and out let valve ports, a rotary cylinder body havin a plurality of annularly arranged parallel pump cylinders with end ports opening to an end, valve face in flat bearing engagement with said first mentioned face, a plurality of pump plungers reciprocable in said cylinders, spring means for urging said plungers outwardly, an axial shaft for driving said body, an angular swash plate coacting with the outer ends of said plungers for reciprocaitng said plungers in uniformly timed sequence upon rotation of said body, said cylinder ports moving successively through communication with said inlet and outlet ports upon move ment of the respective plungers through their intake and pressure strokes, a hydraulic balancing plunger acting on said swash plate in a direction to decrease the inclination of said plate, and being responsive to the delivery pressure of the pump whereby to counterbalance the reaction of said pressure in said cylinders on said plungers, and a hydraulic control plunger acting on said swash plate in a direction to decrease the inclination of said plate and being adapted for response to a selectively variable control pressure whereby to control the displacement of the pump.

3. A pump comprising, in combination, a stationary valve member having an end valve face with peripherally spaced arcuate inlet and outlet valve ports, a rotary cylinder body having a plurality of annularly arranged parallel pump cylinders with end ports opening to an end valve face in flat bearing engagement with said first mentioned face, a plurality of pumpplungers reciprocable in said cylinders, spring mean for urging said plungers outwardly, an axial shaft for driving said body, an angular swash plate coacting with the outer ends of said plungers for reciprocating said plungers in uniformly timed sequence upon rotation of said body, said cylinder ports moving successively through communication with said inlet and outlet ports upon movement of the respective plungers through their intake and pressure strokes, a hydraulic balancing plunger acting on said swash plate in a direction to decrease the inclination of said plate, and being responsive to the delivery pressure of the pump whereby to counterbalance the reaction of said pressure in said cylinders on said plungers, a hydraulic control plunger acting on said swash plate in a direction to decrease the inclination of said plate and being adapted for response to a control pressure whereby to control the displacement of the pump, and a positive stop for limiting the maximum angularity of said plate to define the maximum displacement of said pump plungers.

4. A pump comprising, in combination, a stationary valve member having an intake and a discharge outlet, a rotary cylinder body having a plurality of parallel cylinders annularly arranged about the axis of rotation and having a rotary valve member coacting with said stationary valve member for connecting said cylinders sucpessively to said intake and discharge outlet, a plurality of pistons reciprocable in said cylinders, spring means in said cylinders tending to urge said pistons outwardly, a swash plate mounted for angular adjustment about an axis extending transversely of said axis of rotation and coacting with said pistons to effect reciprocation of said pistons in timed sequence upon rotation of said body, a balancing plunger responsive to the discharge pressure of said pump and coacting with said swash plate in a direction to counteract the hydraulic reaction on said pistons, and a second hydraulic plunger coacting with said swash plate in opposition to said spring means and adapted to adjust the angularity of said swash plate in response to variations in a control pressure whereby to adjust the displacement of said pistons.

5. A pump comprising, in combination, a sta tionary valve member having an intake and a discharge outlet, a rotary cylinder body having .a plurality of parallel cylinders annularly arranged about the axis of rotation and having a rotary valve member coacting with said stationary valve member for connecting said cylinders successively to said intake and discharge outlet, a plurality of pistons reciprocable in said cylinders, spring means in said cylinders tending to urge said pistons outwardly, a swash plate mounted for angular adjustment about an axis extending transversely of said axis of rotation and coacting with said pistons to efiect reciprocation of said pistons in timed sequence upon rotation of said body, a housing structure formed with two parallel cylinder bores located at equal distances from said axis of said swash plate, the inner end of one of said bores being directly and constantly connected to the pressure discharge of the pump, a balancing plunger responsive to the discharge pressure of the pump and coacting with said swash plate in a direction to counteract the hydraulic reaction on said pistons, the other bore having a pressure control port adapted for connection to a source of a variable control pressure, and a second hydraulic plunger reciprocable in said other bore and coacting with said swash plate in opposition to said spring means and adapted to adjust the angularity of said swash plate in response to variations in said control pressure whereby to adjust the displacement of said pistons.

6. A pump comprising, in combination, a stationary valve member having an intake and a discharge outlet, a rotary cylinder body having a plurality of parallel cylinders annularly arranged about the axis of rotation and having a rotary valve member coacting with said stationary valve member for connecting said. cylinders successively to said intake and discharge outlet, a plurality of pistons reciprocable in said cylinders, spring means in said cylinders tending to urge said pistons outwardly, a swash plate mounted for angular adjustment about an axis extending transversely of said axis of rotation and coacting with said pistons to efiect reciprocation of said pistons in timed sequence upon rotation of said body, a housing structure formed with two parallel cylinder bores located at equal distances from said axis of said swash plate, the inner end of one of said bores being directly and constantly connected to the pressure discharge of the pump, a balancing plunger responsive to the discharge pressure of the pump and coacting with said swash plate in a direction to counteract the hydraulic reaction on said pistons, the other bore having a pressure control port adapted. for connection to a source of a variable control pressure, a second hydraulic plunger reciprocable in said other bore and coacting with said swash plate in opposition to said spring means and adapted to adjust the angularity of said swash plate in response to variations in said control pressure whereby to adjust the displacement of said pistons, and a stop plug inserted in said second bore inwardly of said port for limiting the maximum angularity of said swash plate so as to define the maximum displacement of said pistons.

MAX A. MATHYS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,424,823 Ingoldby Aug. 8, 1922 1,840,866 Rayburn et al Jan. 12, 1932 2,299,234 Snader et al Oct. 20, 1942 2,299,235 Snader et al Oct, 20, 1942 2,416,339 Mathys Feb. 25, 1947 2,455,062 Ifield Nov. 30, 1948 2,459,786 Beaman Jan. 25, 1949 

